Axial impact type tang break-off tool



prl 29, 1952 o, FORSTER 2,594,901

AXIAL IMPACT TYPE TANG BREAK-OFF TOOL Filed July 25, 1950 .BYWQM Patented Apr. 29, 1952 AXIAL IMPACT TYPE TANG BREAK-OFF TOOL John 0. Forster, Long Island City; N. Y., assignor to Heli-Coil Corporation, Long Island City, N. Y., a corporation of Delaware Application July 25, 1950, Serial No. 175,693

8 Claims. (Cl. 81-52.35)

The present invention relates to a tool for breaking off the tang of a wire coil insert for a screw-connection. Wire coil screw thread inserts are usually provided with a diametrical y tang required as a grip for a tool for screwing the insert into a tapped hole. In many instances, particularly if a through-going 'hole is lined with such a wire coil the tang 'must be removed after the insertion as otherwise it wou1d interfere with a bolt or screw engaging the insert.

vInA order to facilitate the breaking of the tang, a notch is conventionally `provided in the wire near the point where the tang joins the adjacent coil convolution. However, when an axial force is exerted on the tang from the inside of the coil to break it off, it frequently happens that the adjacent convolution is deformed and bent out of its seat in the thread groove which it lines.

Therefore it is an object of the present invention to provide a tool for breaking-off the tang, which includes means to prevent a deformation of the coil convolutions.

-It also happens that a force applied to break ofi the tang is either too weak causing merely a bend or it is too strong which may cause other unforeseen damage.

The invention further aims, therefore, to provide a tool of the mentioned type in which a predetermined or adjustable force can be applied to the tang in order to break it oif.

The invention essentially consists of a pilot sleeve of an outer diameter similar to the i'nner Fig. 5 is an end elevation of a part of the tool of Fig. 2,and

Fig. 6 is a cross-section along line 6--6 of Fig. 2.

Referring now to Fig. l, the tool in general denoted by I0 is shown inserted in a wire coil II which lines the tapped threading I2 of a hole I3 in a member I4. The coil has been inserted from the surface I5 and its diametrically directed tang I6 constitutes the continuation of the adjacent end convolution I'I. The tool I0 comprises a pilot sleeve I8 having an outer diameter similar to that means very slightly smaller than the inner diameter of the coil I I for which it is destined. This outer diameter is preferably so selected that the pilot sleeve can be easily inserted but with only little clearance between it and the convolutions of the coil. Al punch I9 4fitting the interior of the pilot` sleeve projects diameter of the coil.into which it may be inserted, and a punch guided in the sleeve and engaging the tang, so that the latter will be broken off when the punch is hit with a hammer, while the sleeve prevents the coil convolutions from being bent out of their seat in the tapped threading lined with the coil. A The invention also consists of a tool of the mentioned type in combination with a hammer which under a spring pressure will strike the punch with a predetermined or adjustable force. .Further objects and details of the invention will be apparent from the description given hereinafter and the accompanying drawing illustrating embodiments thereof by way of example. In the drawing, Fig. 1 isV a longitudinal cross-section of a too according to the invention, Y Fig. 2 is a longitudinal cross-section of another embodiment including a hammer tov strike the punch,

therefrom with its head 2U and is substantially longer than the sleeve. Preferably, the punch I9 has a foot portion 2I either integral with the punch shank 22 or produced as a separate piece and inserted into the .shank end as shown at 23. If such foot 2| is provided it should have a diameter similar to the outer diameter of the sleeve. Furthermore -it is advisable to make the foot frustro-conical so as to t an inner taper of the pilot sleeve as clearly shown at 2| in order to insure that the pilot sleeve engages, from the interior all the coil convolutions. up to the tang. However, it is also possible to do without the foot portion 2i, meaning that the end of the punch is of a diameter similar tothat of the 'shank 22. Such structure is less recommendable because it may happen that the slim punch end bends the tang sideways and bypasses rather than break it off.

Now in order to break ofi the tang I6 the sleeve I8 with the punch I9 will vbe introduced into the coil I I until the foot 2l bears 0n the tang and the sleeve endbears on the foot. In this position of the coil, the coil convolutions are flrmlyheld within the grooves of thevtapped threading and cannot yield to a force tending to bend themA towards the axis of the hole I3. If, then, thepunch head 2li is hit by a hammer with the required force the tang can be broken off without injury to the coil convolutions.

Now, I have found that the tang may be bent when the sleeve is introduced into the coil with V too much pressure, before the punch is hit with a hammer, and, that in such an event the tang does not readily break off. lIn orderto avoid such happening, -I provide anothersleeve 2 4 in 3 which the .pilot sleeve I8 is telescopically shiftable so as to project a variable length from the end face of the sleeve 24. Near the opposite end of sleeve 24 an inner shoulder 26 is provided between Which and the pilot sleeve a compression spring 21 is located. The head end 29 of the punch projects a distance from that opposite end of sleeve 24. Means engaging both sleeves prevent their separation. For that purpose, a pin or screw 28 is secured in the Wall of sleeve 24 and engages in a longitudinal groove 29 of sleeve I8, which groove terminates at a short distance from the inner end 1 face V.'30 .of said sleeve. Now it will .be clear that upon introduction of the tool in a coil II, spring 21 will be compressed with the tang is reached, until nnally the end face 25 of sleeve 24 bears on the surface I5. As the spring 21 can be selected sufliciently soft no excessive pressure can be exerted on the tang by the sleeve I8 or the punch foot 2I projecting therefrom before thepunch Vis hit.

Insert coils of the kind here under consideration generally' are of a very hard and,jto.an` extent, even brittle material which breaks more .readily under a short, brisk blow than under-a more slowly acting pressure. However, owing to the strength of the material the hammer stroke must not be toc light nor too strong. Ingthat respect faulty operation can be avoidedlbythe combination of a tool of the type'just .described with a hammer mechanism striking the punch with the desired strength and. briskness. Such a combined tool is illustrated in Figs'. 2 to 5. ,This tool comprises a pilot sleeve withapunchSI guided therein. The punch has'a foot 32, and an elongated shank 33 ending in a head 34. The pilot sleeve 30 is telescopically shiftable in a second sleeve 35, and prevented from separating therefrom by its ilange-like rim 36 which can abut against a ring 31 secured in thel adjacent end of the sleeve 35. 'The latter has a .tubular extension 38 which also guides the punch shank 33, and is telescopi-cally Shiftable `in an outer sleeve 39. A split spring ring 49 with a radially inward projecting pin 4I is embedded in thewall of the sleeve 39, and the pin engages a longitudinal groove 42 in the wall of the sleeve 35, thereby preventing separation of sleeve from sleeve 39. Within the latter a cylindrical hammer 43 is axially Shiftable. Movement of the hammer towards the side of the other sleeves is limited by an inner shoulder 44 of sleeve 39 again-st which a flange-like rim 45 of the hammer can abut. The hammer has a blind axial bore 45 through the major part of its length and open towards the sleeve 35. The diameter of the bore is equal to the outer diameter of the tubular extension 38 of sleeve 35. Near the open end of the bore 43 the hammer is provided with a diametrical bore 41 into which a detent'member 48 slidably ts. The detent which is somewhat shorter than the inner diameter of sleeve`39, has a bore -49 in the lengthwise direction of the sleeves. The diameter of bore 49 is equal to that of the ybore 45 of the hammer. cured to the hammer at 5I in a groove BI' thereof A leaf spring 59 is seand engages the detent in a slot 62 clearly shown in Fig. 5, thus preventing the detent from turning and tending to urge the detent in the direction of its rounded head 52. At a distance from .the head. 52, inthe position of Fig.`2, .there is a .second inner shoulder 59 provided in sleeve 39 4 shift of the hammer, the head 52 engages that shoulder. The open end of the sleeve 39 is provided with a threading 53 engaged by a screw cap 54, and a compression spring 55 is arranged between that cap and the hammer and can be Vprei-tensionedas desired'byturningthe cap in vrelation to thesleeve 39.

Another'. compression spring 5S is located between sleeve 35 and a washer 51 bearing against the hammer, and a .third compression spring 58 is provided interiorly of sleeve 35 and bears against the pilot sleeve 33 in a manner similar to the spring 21 t-in;Fig. 1. Spring 56 is much more exible than spring-55. but somewhat stronger than spring 58.

When the vtool is not in use the parts are in theposition of Fig. 2. In that position the hammer is pushed by spring 55 with its flange 45 against shoulder 44, and the sleeves 35 and 39 are projected as far as possible under the action of the vsprings 56 and 58 respectively. Thehead v34 with the adjacentgportion of shank 33 projects through the `bore'49 of the detent a short distance into the bore46 oftheV hammer. 'As the detent 48 under the 4pressure of its'spring59 is in such a position that its bore 49 is eccentric with respect to the axeslof the sleeves, the end of thetubular extension 38 bears against the detent 48. Intthe illustratedfembodiment, the extension engages the continuation of thebore 46 in the adjacent very shortend--portion'63.ofthe hammer. This aids in .ensuring co-axial align vment of the parts. .However, other arrange- ;ments are conceivable wherein there is no such end portion 63, as it iszmerely. essentialthatin the position of Fig..2 the extension 38 cannot enter the bores 49. and 46.

By gripping-sleeve 39rwhile the-parts are'in the position of Fig. 2, the tool may be inserted with its pilot sleeve 3D into a coil such as the coil II in Fig.: 1. When the' tangof the coil resists further advancement of thev pilot sleeve: and

tom 54 of the bore 46 even if sleeve 30 is shifted its maximum distance into sleeve 35. `Such clearance should exist under all conditions prior to the release of the hammer. Continued pushing of ysleeve 39 in the direction of the other sleeves will cause a shift of the hammer towards the cap 54 owing to the tubular extension 38 pressing against the detent 48. Thereby, spring 55 will be tensioned.

It willbe clear that during such shift the-hammer and the punch will not change their vrelative position, nor will spring 56 he compressed.

When the hammer 43 in its movement relative to sleeve 39 in the direction1of arrow` a reaches the position of Fig.3 and the head52 .of the detentengages the inclinedA shoulder't, the detent willbe shifted so that .thebores 46 and 49 register and the tubular extension'38 can enter the bore 49 and continue into. the vbore. ,46. Thereby the pressure against theihammer 43 is suddenly removed so ,that the hammerwill be pushed by spring 55 in the. direction of arrow4 b of Fig. 4 and hit the punch'head34 with the bottom 65 of its bore d6. As the stroke of the hammer depends on the spring 55 a desired irnpact can be attained by a suitable selection of the spring characteristics, and by an adjustment o`f the cap 5:3. 1n the operation of the hammer, spring 55 has a certain cushioning effect which is to be taken into consideration in the dimensioning of spring 55.

When the tang has been broken off, the tool can be removed from the coil, whereupon spring 53 will project the pilot sleeve with its flange 35 to bear on ring 3l', and spring 56 will urge sleeve 35 into its end position. Thereby the extension 38 will be withdrawn from the bore 49 of the detent 43 which under the action of spring 50 will return to its eccentric-position, so that all parts take again the position of Fig. 2.

t will be apparent to those skilled in the art that many alterations and modications of the structure shown and described are possible without departure from the essence and spirit of my invention which for that reason shall not be limited but by the scope of the appended claims.

I claim:

1. A tool for breaking oli the tang of a screw thread wire coil, comprising a iirst sleeve having an inner shoulder near one of its ends, a pilot sleeve telescopically shiftable in said rst sleeve so as to project from the other end of said rst sleeve, said pilot sleeve havingan outer diameter slightly smaller than the inner diameter of the coil for which the tool is designed, a compression spring between said shoulder and said pilot sleeve, interengaging means in connection with both said sleeves to prevent projection of said pilot sleeve beyond a predetermined length from said first sleeve and a punch projecting from said first mentioned end of said rst sleeve and being projectable from the opposite end of said pilot sleeve, said punch being guided in said pilot sleeve, and freely shiftable within limits in axial direction with respect toboth said sleeves.

2. A tool as claimed in claim 1, said punch having a length greater than the combined length of said rst sleeve and the projectable portion of said pilot sleeve, and including a frustro-conical foot substantially tting an inner taper of the free end of said pilot sleeve.

3. A tool as claimed in claim 1, wherein said punch is retractable into said pilot sleeve at least so far that its end face is iiush with that end face of said pilot sleeve which is remote from said rst sleeve.

4. A tool for breaking oi the tang of a screw thread wire coil, comprising a first sleeve having an inner shoulder, a pilot sleeve telescopically shiftable in said rst sleeve and having an outer diameter slightly smaller than the inner diameter of the coil for which the tool is designed, a compression spring between said shoulder and said pilot sleeve, interengaging means in connection with both said sleeves to prevent projection of said pilot sleeve beyond a predetermined length from said irst sleeve, a punch guided in said iirst sleeve, an outer sleeve in which said first sleeve is telescopically shiftable so as to be projectable together with said pilot sleeve from one end of said outer sleeve, a hammer shiftable within said outer sleeve and adapted to strike said punch, a second compression spring between said hammer and the other end of said outer sleeve, a lost motion connection including a detent between said first sleeve and said hammer whereby said hammer will be shifted against the restraint of said second spring when said rst sleeve is pushed inward with respect to said outer sleeve, and means to release said detent when said second spring is tensioned, thereby causing said hammer to move under the action of said second spring relatively to said first sleeve and to strike said punch.

5. A tool as claimed in claim 4, wherein said lost motion connection includes a tubularextension of said first sleeveA from which the head of the punch projects, said hammer being provided with an axial blind bore into which said tubular extension and said punch head can enter, and said detent when in detaining position being adapted to bar the entrance of said projection into said bore, and when released to open said entrance.

6. A tool as claimed in claim ll, further comprising a third compression spring more liexible than said second but stronger than said irst spring, said third spring being arranged between said iirst sleeve and said hammer.

7. A tool as claimed in claim 4, further comprising a screw member in connection with said other end of said outer sleeve, and co-aXial therewith, said second spring bearing against said screw member.

8. A tool for breaking oil the tang of a screw threadwire coil, comprising a first sleeve having an inner shoulder, a pilot sleeve telescopically shiftable in said irst sleeve and having an outer diameter slightly smaller than the inner diameter of the coil for which the tool is designed, a compression spring between said shoulder and said pilot sleeve, interengaging means in conneotion with both said sleeves to prevent projection of said pilot sleeve beyond a predetermined length from said first sleeve, a punch guided in said iirst sleeve, an cuter sleeve in which said iirst sleeve is telescopically shiitable so as to be projectable together with said pilot sleeve trom the one end of said outer sleeve, a hammer axially shiftable in said outer sleeve, a second compression spring between the other end of said outer sleeve and said hammers, said hammers being provided with a blind axial bore in the end corncronting said iirst sleeve', said rst sleeve including an axial tubular extension from which the head of said punch projects and which is adapted to enter said bore, a detent member, a third spring biasing said detent which to guided in said hammer for movement transverse thereto and barring the entrance into the bore, said outer sleeve and said detent including abutment faces to shift said detent into a position in which said entrance is open when said second spring is tensioned, and a fourth compression spring more eXible than said second and stronger than said iirst spring between said hammer and said rst sleeve.

JOHN O. FORSTER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 863,909 Evans Aug. 20, 1907 1,572,046 Seiler Feb. 9, 1926 1,720,318 Chisholm July 9, 1929 1,952,395 Tillyer et al. Mar. 27, 1934 2,455,270 Ravella Nov. 30, 1948 FOREIGN PATENTS Number Country Date 610,208 Great Britain Oct. 13, 1948 

